Shield and spring interface to a spark plug from a pencil coil

Abstract

An interface device for interfacing a pencil coil to a spark plug is provided. The interface device comprises a substantially C-shaped spring adapted to mechanically and electrically engage a pencil coil shield and also adapted to make electrical contact with a spark plug ground while the spring remains mechanically and electrically engaged to the pencil coil shield. Also provided is a pencil coil shield assembly for interfacing a pencil coil to a spark plug. The pencil coil shield assembly comprises a substantially cylindrical pencil coil and a spring. The substantially cylindrical pencil coil shield is adapted to surround the pencil coil. The spring is mechanically and electrically engaged with the pencil coil shield and is adapted to make electrical contact with a spark plug ground while the spring remains mechanically and electrically engaged to the pencil coil shield. The interface device and/or pencil coil shield assembly can be configured to reduce RFI from the secondary current winding currents of a pencil coil. In addition, each can be manufactured using inexpensive and uncomplicated manufacturing and installation techniques, and using starting materials and parts that are relatively inexpensive. Also provided is a method of reducing RFI from secondary winding currents of a pencil coil by, among other things, electrically connecting the substantially cylindrical shield to a low voltage terminal of a secondary winding of the pencil coil, and electrically connecting the substantially cylindrical shield to a spark plug ground of a spark plug associated with the pencil coil.

What is claimed is:  
     
       1. An interface device for interfacing a pencil coil to a spark plug comprising: 
       a substantially C-shaped spring adapted to mechanically and electrically engage a pencil coil shield and also adapted to make electrical contact with a spark plug ground while the spring remains mechanically and electrically engaged to the pencil coil shield.  
     
     
       2. The interface device of  claim 1 , wherein said spring has radially inward protuberances adapted to mechanically and electrically engage a spark plug ground. 
     
     
       3. The interface device of  claim 2 , wherein the protuberances are spaced apart from one another by about 210 degrees about the circumference of the substantially C-shaped spring. 
     
     
       4. The interface device of  claim 2 , wherein the protuberances are located near distal ends of the substantially C-shaped spring. 
     
     
       5. The interface device of  claim 4 , wherein the protuberances are located near distal ends of the substantially C-shaped spring and are spaced apart from one another by about 210 degrees about the circumference of the substantially C-shaped spring. 
     
     
       6. The interface device of  claim 2 , wherein the substantially C-shaped spring is made from sheet metal that has been reconfigured to provide the C-shape of the spring. 
     
     
       7. The interface device of  claim 6 , wherein each of the protuberances is defined by a radially inward bend in the sheet metal. 
     
     
       8. The interface device of  claim 1 , wherein the substantially C-shaped spring has a diameter substantially equal to an inside or outside diameter of the shield. 
     
     
       9. A pencil coil shield assembly for interfacing a pencil coil to a spark plug comprising: 
       a substantially cylindrical pencil coil shield adapted to surround a pencil coil;  
       a spring mechanically and electrically engaged with the pencil coil shield and adapted to make electrical contact with a spark plug ground while the spring remains mechanically and electrically engaged to the pencil coil shield.  
     
     
       10. The pencil coil shield assembly of  claim 9 , wherein said spring is substantially C-shaped and has radially inward protuberances adapted to mechanically and electrically engage a spark plug ground. 
     
     
       11. The pencil coil shield assembly of  claim 10 , wherein the protuberances are spaced apart from one another by about 210 degrees about the circumference of the spring. 
     
     
       12. The pencil coil shield assembly of  claim 10 , wherein the protuberances are located near distal ends of the spring. 
     
     
       13. The pencil coil shield assembly of  claim 12 , wherein the protuberances are located near distal ends of the spring and are spaced apart from one another by about 210 degrees about the circumference of the spring. 
     
     
       14. The pencil coil shield assembly of  claim 10  wherein the spring is made from sheet metal that has been reconfigured to provide the C-shape of the spring. 
     
     
       15. The pencil coil shield assembly of  claim 14 , wherein each of the protuberances is defined by a radially inward bend in the sheet metal. 
     
     
       16. The pencil coil shield assembly of  claim 9 , wherein the spring is substantially C-shaped and has a diameter substantially equal to an inside or outside diameter of the shield, the spring being arranged with respect to the shield so that a portion of a major surface of the shield bears against a major surface of the spring. 
     
     
       17. The pencil coil shield assembly of  claim 16 , wherein said major surface of the shield is an outer surface of the shield and said major surface of the spring is an inside surface of the spring. 
     
     
       18. The pencil coil shield assembly of  claim 17 , wherein said spring has radially inward protuberances adapted to mechanically and electrically engage a spark plug ground; and 
       wherein the shield has openings aligned with the protuberances, through which said protuberances extend to make contact with a spark plug ground.  
     
     
       19. The pencil coil shield assembly of  claim 9 , wherein said shield is electrically connected to a low voltage terminal of a secondary winding of a pencil coil so that a return path for a secondary winding current is established from a spark plug ground, through the spring, through the shield, and into the low voltage terminal, when the spring makes electrical contact with the spark plug ground. 
     
     
       20. The pencil coil shield assembly of  claim 9 , wherein said pencil coil shield includes a main substantially cylindrical body and a ring-shaped spring mount that is connected to the substantially cylindrical body by an extension of the body. 
     
     
       21. The pencil coil shield assembly of  claim 20 , wherein said spring is engaged to the ring-shaped spring mount. 
     
     
       22. The pencil coil shield assembly of  claim 20 , wherein said ring-shaped mount is coaxially arranged with respect to the substantially cylindrical body. 
     
     
       23. The pencil coil shield assembly of  claim 20 , wherein said spring is substantially C-shaped and has radially inward protuberances adapted to mechanically and electrically engage a spark plug ground; and 
       wherein the ring-shaped mount of the shield has openings aligned with the protuberances, through which said protuberances extend to make contact with a spark plug ground.  
     
     
       24. The pencil coil shield assembly of  claim 9 , wherein said spring, is provided in the form of at least one tab that extends from the shield in a substantially radially inward direction to make electrical contact with a spark plug ground. 
     
     
       25. The pencil coil shield assembly of  claim 24 , wherein said at least one tab is substantially hook-shaped. 
     
     
       26. The pencil coil shield assembly of  claim 24 , wherein said at least one tab comprises a plurality of tabs spaced apart from one another symmetrically about a circumference of the shield. 
     
     
       27. The pencil coil shield assembly of  claim 26  wherein said plurality of tabs are arranged with respect to one another about the shield in such a way that, when said spring is applied to a spark plug ground that has a generally hexagonal shape and in such a way that one of the tabs engages an apex of the generally hexagonal shape, others of said tabs also engage other apexes of the generally hexagonal shape. 
     
     
       28. A pencil coil shield assembly for interfacing a pencil coil to a spark plug comprising: 
       a substantially cylindrical pencil coil shield adapted to surround a pencil coil;  
       means mechanically engaged to the pencil coil shield, for electrically connecting the pencil coil shield with a spark plug ground.  
     
     
       29. A method of reducing RFI from secondary winding currents of a pencil coil, said method comprising the steps of: 
       providing a substantially cylindrical shield around a pencil coil;  
       electrically connecting the substantially cylindrical shield to a low voltage terminal of a secondary winding of the pencil coil; and  
       electrically connecting the substantially cylindrical shield to a spark plug ground of a spark plug associated with the pencil coil.  
     
     
       30. The method of  claim 29 , wherein said step of electrically connecting the substantially cylindrical shield to a spark plug ground is performed using a spring so that a direct return path for a secondary winding current is established from the spark plug ground, through the spring, through the shield, and into the low voltage terminal, when the spring makes electrical contact with the spark plug ground. 
     
     
       31. The method of  claim 30 , wherein said step of electrically connecting the substantially cylindrical shield to a spark plug ground is performed on a hexagonal portion of the spark plug ground. 
     
     
       32. The method of  claim 31 , wherein said step of electrically connecting the substantially cylindrical shield to a spark plug ground is performed in such a way that spring variance in deflection is limited to less than 4% during any axial rotation of the shield.